Answer:
Sarcomere.
Explanation:
Sarcomere is responsible for the striation of the skeletal and cardiac muscle. The striation was first described by the scientist Van Leeuwenhoek.
Sarcomere may be defined as the basic unit of the striated muscle tissue. This is the repeating unit of two Z lines alternating between the dark and light bands of the striated muscle.
Thus, the answer is sarcomere.
